Two observable features of the staggered-flux phase at nonzero doping

Hsu, T. C.; Marston, J. B.; Affleck, Ian

doi:10.1103/physrevb.43.2866

Cited by 131 publications

(134 citation statements)

References 39 publications

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“…4, 5 Chakravarty et al 6 have suggested that the pseudogap stems from a hidden order denoted by a d-density-wave (DDW) phase that competes with superconductivity and explains in a natural way the doping dependence of T C . This state is similar to circulating currents around the Cu-O bonds resulting from the staggered flux phase of the t-J model introduced by Hsu et al 7 These currents would produce a small magnetic field directed largely along the c-axis of the superconducting crystal and should be visible in a sufficiently accurate neutron scattering experiment. 8 Here we present data demonstrating the present capability to observe such a state and show that the best measurements suggest the possibility of such a state rather than showing a null result.…”

supporting

confidence: 62%

Polarized neutron measurement of magnetic order inYBa2Cu3O6.45

et al. 2004

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Orbital current order of the d-density-wave type (DDW) has been postulated to explain the pseudogap in the high temperature superconductors. We have performed neutron scattering experiments to search for this order and show here the results obtained on an YBa 2 Cu 3 O 6.45 sample using the best neutron spectrometers available. We argue that the data are consistent with a small, largely c-axis-directed moment, found below about 200K.PACS numbers: 72.15. Gd, 61.12.Ld, 71.30.+h 2 The microscopic origin of the pseudogap is one of the most puzzling attributes of the cuprate superconductors. A review of the various experimental techniques used to determine the pseudogap is given by Timusk and Statt. 1 It is generally considered to stem from pairing above the superconducting transition temperature T C 2,3 or result from another ground-state differentiated from superconductivity by a quantum critical point. 4,5 Chakravarty et al. 6 but a competing phase judged to stem from impurities made the identification of the DDW state difficult. The moments from the bond currents result in peaks at the (h/2, k/2, l) superlattice positions of the reciprocal lattice. This is the position that magnetism is found in the parent compound, YBa 2 Cu 3 O 6.15 , which is an insulator with a Néel transition temperature well above room temperature and has been studied previously. 10,11 The defining attribute of the DDW state is that the moment should be largely along the c-axis. Small moments in the sample crystal originating from the parent compound should be located in the a-b plane as is found for this material. Other magnetic impurity phases could be possible, but to our knowledge no such phases 3 are known to have high temperature (above 50K) magnetic order along the c-axis for the YBa 2 Cu 3 O 6+x system.In order to determine the direction of the moments for the antiferromagnetic state it is necessary to use polarized neutrons, as outlined by Moon et al. in 1969. 12 The crystal used in the experiments is twinned so that a* could not be differentiated from b*. We thus consider the crystal to be tetragonal so that the (1, 1, 0) reflection showed no peak indicating that the higher order scattering from the monochromator was well removed. Figure 1b shows the result of a HF SF measurement through the (1/2, 1/2, 1) position at 20 K. The scan range on the high Q side of the scan is limited by intense NSF scattering that is difficult to correct for with the rather small flipping ratio as seen in Fig 3a. Nevertheless, a peak is observed at (0.5, 0.5, 1) and a Gaussian fit results in a height of 11±2 counts with a width of 0.01±0.002 FWHM at the position 0.5±0.001 r.l.u. The peak is resolution limited, giving a correlation length of about 380Å. Figure 1c shows no evidence for a peak at a temperature of 150K. Multiple runs were averaged to obtain the observed error bars. 5These scans took over two days each and are difficult to improve in a reasonable time period.Also, since the magnetic signal is so small, a higher flipping ratio is des...

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confidence: 62%

Polarized neutron measurement of magnetic order inYBa2Cu3O6.45

et al. 2004

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“…This relation follows from the symmetry of the momentum sum and Equation 15. The structure factor in Equation 42 takes the same value at the two smallest scattering angles corresponding to the points Q 2 b = (π, 0, π) and Q 4 b = π in the reciprocal lattice:…”

Section: Neutron Scatteringmentioning

confidence: 95%

Three-dimensional flux states as a model for the pseudogap phase of transition metal oxides

Schroeter

Doniach

2002

Phys. Rev. B

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We propose that the pseudogap state observed in the transition metal oxides can be explained by a three-dimensional flux state, which exhibits spontaneously generated currents in its ground state due to electron-electron correlations. We compare the energy of the flux state to other classes of mean field states, and find that it is stabilized over a wide range of t and δ. The signature of the state will be peaks in the neutron diffraction spectra, the location and intensity of which are presented. The dependence of the pseudogap in the optical conductivity is calculated based on the parameters in the model. PACS numbers: 71.10.Fd, 71.30.+h, 75.10.Lp The motivation for this work is the observation of a pseudogap that opens up in optical conductivity measurements of the three-dimensional transition metal oxide SrRuO 3 [1] above its ferromagnetic transition temperature of T C ≈ 150 K. A pseudogap has also recently been seen in BaRuO 3 [2]. In this pseudogapped regime, ρ (T ) increases linearly with temperature, passing through the Ioffe-Regel limit without saturation [3], behavior indicative of a "bad metal" [4]. The optical conductivity in this state is proportional to the non-Fermi liquid behavior of ω −1/2 at high frequency and has a peak at low frequencies [1] at approximately 250 cm −1 , the precise location of the peak being temperature dependent.We propose that this pseudogap state can be understood by considering a ground state with spontaneously generated electronic currents circulating around the plaquettes. The currents arise from electron-electron correlations, due to the bi-quadratic terms in the Hamiltonian. The state which we propose is a generalization of the two-dimensional flux states invented by Affleck and Marston [5], and studied in their chiral extension by Wen, Wilzcek, and Zee [6]. Unlike the two-dimensional case, there is no possibility of fractional statistics in three dimensions. However, the spontaneous generation of gauge fields is a possibility in three dimensions, and these gauge fields can lead to a ground state with circulating electronic currents. Earlier work was done on three-dimensional flux states by Laughlin and coworkers [7,8] and Zee [9].In actuality, SrRuO 3 has 5 bands crossing the Fermi surface formed by hybridizing the Ruthenium d orbitals with the Oxygen p orbitals [10]. The crystal structure is orthorhombic, becoming cubic at temperatures greater than 900 K [11]. Undoubtedly, the actual electronic structure of SrRuO 3 , and particularly the presence of a van Hove singularity near the Fermi surface, influence the material's behavior. The model which we consider is vastly simplified and serves as a starting point for consid- * Electronic address: dfs@Stanford.edu ering the nature of the pseudogapped state in the threedimensional transition metal oxides. A model which incorporates some of these electronic features, but does not focus on the pseudogap regime, has been proposed by . I. MODEL SYSTEMThe Hamiltonian that we consider is the single orbital t-J model given byw...

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“…The muons in a µSR experiment might see a lowwer field if they sit at points of high symmetry or away from the plane. The orbital magnetic moments are likely to be dwarfed by local spin moments [3]. Incommensurate ordering may or may not break T ; if it does, the above analysis applies.…”

Section: Experimental Signaturesmentioning

confidence: 96%

Density-wave states of nonzero angular momentum

2000

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We study the properties of states in which particle-hole pairs of non-zero angular momentum condense. These states generalize charge-and spin-density-wave states, in which s-wave particlehole pairs condense. We show that the p-wave spin-singlet state of this type has Peierls ordering, while the d-wave spin-singlet state is the staggered flux state. We discuss model Hamiltonians which favor p-wave and d-wave density wave order. There are analogous orderings for pure spin models, which generalize spin-Peierls order. The spin-triplet density wave states are accompanied by spin-1 Goldstone bosons, but these excitations do not contribute to the spin-spin correlation function. Hence, they must be detected with NQR or Raman scattering experiments. Depending on the geometry and topology of the Fermi surface, these states may admit gapless fermionic excitations. As the Fermi surface geometry is changed, these excitations disappear at a transition which is thirdorder in mean-field theory. The singlet d-wave and triplet p-wave density wave states are separated from the corresponding superconducting states by zero-temperature O(4)-symmetric critical points.

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Two observable features of the staggered-flux phase at nonzero doping

Cited by 131 publications

References 39 publications

Polarized neutron measurement of magnetic order inYBa2Cu3O6.45

Polarized neutron measurement of magnetic order inYBa2Cu3O6.45

Three-dimensional flux states as a model for the pseudogap phase of transition metal oxides

Density-wave states of nonzero angular momentum

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